1. Field of the Invention
This invention relates to a digital-to-analog (D/A) converter suitable for use where a video signal digitally processed in a video camera or the like is convened into an analog signal.
2. Prior Art
In particular this invention relates to a digital-to-analog converter having a ladder resistor portion for generating a plurality of quantization signals of predetermined values based on a reference signal and a quantization switch portion for selectively outputting one of the quantization signals in accordance with a digital input value.
Such a digital-to-analog converter is known from U.S. Pat. No. 5,079,552.
In accordance with the recent expansion of the application field of the digital signal processing IC's, a significant progress has been achieved in the digital processing of video signals in consumer-use portable apparatuses such as portable video cameras (or camcorders). The video signal digitally processed in such a camcorder is generally convened into an analog video signal by a D/A converter in order to obtain a standard analog recording signal.
A luminance signal, for example, of the video signal in such a digital signal processing IC as described above is usually represented in eight bits and is converted into an analog signal by means of a D/A converter incorporated in the IC. The analog luminance signal thus obtained and outputted from the IC is combined with a synchronization signal with the aid of other circuit components and is thereafter supplied, for example, to a frequency converter.
It would not be very efficient in the miniaturization of a camcorder or the like to provide separate circuit components, in addition to the digital processing IC, only for the purpose of adding a synchronization signal as described above. On the other hand, for the incorporation of a synchronization-signal, addition circuit into a digital video signal processing IC, a special measure has to be taken to overcome the restrictions of space in the IC.